1. Field of the Invention
The present invention relates to a composite film having a protective layer containing an inorganic silicate having a layered structure on at least one surface thereof.
2. Description of the Related Art
Although various composite films having a protective layer containing an inorganic substance have been known up to this time, the inorganic substances used are generally granular, so that the protective layer has disadvantages in that the covering properties are insufficient and that the surface of the layer tends to become rough. Further, the use of a silicate having a layered structure is disclosed in, for example, U.S. Pat. Nos. 4,342,814, 4,131,589 and 4,131,588. However, in these patents, an unswellable mica having a small aspect ratio and a large thickness is used as a silicate, so that no desired effect can be obtained, if the amount of the mica added is small or if the thickness of the protective layer is small.
The use of a swellable silicate having a layered structure is disclosed in, for example, U.S. Pat. Nos. 4,425,465; 4,361,622; 3,784,499 and 3,669,733. However, in these patents, only the flame proofness and heat resistance of the silicate which are characteristics of general as inorganic flakes are noted. On the other hand, though an inorganic film made of a swellable silicate having a layered structure is disclosed in, for example, Japanese Patent Laid-Open No. 223218/1984, it has a disadvantage in that the handling of the silicate is troublesome because of its low cohesive force among flakes.
The inventors of the present invention have succeeded in imparting excellent electrical characteristics, antistatic properties, slipperiness or dazzle-proofness to a composite film by making its protective layer of a mixture comprising an inorganic swellable silicate having a layered structure and a specified compound, and further by using a specified ion as an interlayer ion of the inorganic swellable silicate having a layered structure.